Process for the production of synthesis gas, cracked hydrocarbon and calcined coke

ABSTRACT

Synthesis gases, cracked hydrocarbons, and calcined coke are produced in a calciner wherein hot combustion gases are passed through the hot coke, hydrocarbons and/or steam are injected into the calciner at a point below the combustion zone but into the soaking area, and the products are drawn out of the soaking area and recovered.

United States Patent Merrill, Jr. et al.

[ 51 July 11, 1972 [54] PROCESS FOR THE PRODUCTION OF SYNTHESIS GAS, CRACKED HYDROCARBON AND CALCINED COKE [72] Inventors: La Vaun S. Merrill, Jr., Englewood; Robert E. Schilson,'Littleton, both of [73] Assignee: Marathon Oil Company, Findlay, Ohio [22] Filed: Sept. 12, 1969 [21] Appl. No.: 857,517

[52] US. Cl. ..260/679 R, 260/683, 252/373, 48/204 [51] Int. Cl ..C07c 11/24 [58] Field of Search ..260/679; 252/373, 372; 48/1 19, 48/204, 206; 208/128 [56] References Cited UNITED STATES PATENTS 405,91 1 6/1889 Rennyson ..49/1 19 277,270 5/1883 Gross ..48/l19 Odell ..201/36 ..20l/29 1,883,744 10/1932 Beardsley. .....208/128 1,865,195 6/1932 Lewis ..208/l28 2,526,696 10/1950 Schutte ..260/679 3,522,170 7/1970 Moser, Jr.. ..20l/36 1,875,253 8/1932 Minotte ..252/372 3,440,177 3/1969 Patton et a1" .....252/373 1,762,100 6/1930 Odell ...48/196 1,841,201 l/l932 Odell ...48/l96 2,721,227 10/1955 Mungen ..260/679 Primary Examiner-Delbert E. Gantz Assistant Examiner-J. M. Nelson Attorney-Joseph C. Herring, Jack L. l-lummel and Richard C. Willson, Jr.

[ ABSTRACT Synthesis gases, cracked hydrocarbons, and calcined coke are produced in a calciner wherein hot combustion gases are passed through the hot coke, hydrocarbons and/or steam'are injected into the calciner at a point below the combustion zone but into the soaking area, and the products are drawn out of the soaking area and recovered.

8 Claims, 3 Drawing Figures PA'TENTEBJUL 1 1 I972 SHEET 10F 2 Fig.1

M/VENTORS LA VAUN S. MERR/LL,JR. 8 ROBERT E. SCH/LSON A r TOR/V5 r P'A'TENTEDJUL 11 m2 SHEET 2 [IF 2 .0 Fig.3

v INVENTORS' LA VAUN s. MERR/LL,JR. a ROBERT E. SCH/LSON ATTORNEY PROCESS FOR THE PRODUCTION OF SYNTHESIS GAS, CRACKED HYDROCARBON AND CALCINED COKE BACKGROUND OF THE INVENTION The Prior Art US. Pat. No. 1,968,053 to Odell discloses a method for increasing the gas synthesizing capacity of a coal carbonizing unit by causing reactions to occur between steam and hydrocarbons prior to and simultaneously with the cooling of the carbonized product, which is usually coke.

US. Pat. No. 3,061,524 to Savage teaches a process for coal gasiflcation and the production of synthesis gas wherein powdered coal is converted to a low volatile char, and substantial portions of CO H H 0, and N are manufactured.

SUMMARY OF THE INVENTION Raw petroleum coke is normally calcined at temperatures averaging about 2,000 to 2,500 F. This invention utilizes the heat generated by hot combustion gases of calcination and heat given off by the hot coke to produce synthesis gases, cracked hydrocarbons, and calcined coke in the following manner: combustion gases such as C0, C H N Ar, etc. are passed (e.g. drawn through the hot coke, e.g. asthe coke piles into the soaking pit; steam and/or hydrocarbon are introduced into the calciner below the combustion zone and products of the invention (i.e. synthesis gases and/or cracked hydrocarbons) are withdrawn after passing through the soaking pit, e.g. withdrawn at temperatures from about 1,000 to about 1,600 F.

Any type of calcining unit, including the rotary hearth calciner, the shaft (retort) calciner, or the electric calciner, may conveniently be modified to effect the invention.

The retort calciner can be modified by removing the exhaust pipe assemblies through which combustion gases are withdrawn, and installing an input pipe at some point below the flame front of the calciner through which steam and/or hydrocarbon are injected into the combustion chamber.

In the rotary hearth calciner, the exhaust stacks can be closed off, the soaking pit lengthened to facilitate the flow of combustion gases through the pile of hot coke, and the steam and/or hydrocarbon piped into the soaking pit at points of input determined by the kind and quality of products desired.

DESCRIPTION OF THE DRAWINGS A better understanding of the invention is obtained by reference to the drawings. FIG. 1 is a front elevation of a retort calciner. The calciner is partially broken to show internal equipment and material movement.

Coke is fed from hopper 2 through valve 4, shown as a star feeder, into retort 6. Valve 4 prevents any substantial pressure leak. Retort 6 is bell-shaped and terminates in the conical bottom portion.

The coke piles and moves downwardly through the retort by gravity flow. An oxidant is distributed throughout the width of the coke via oxidant input pipe 8 and header 10.

The coke passes into combustion zone 12, indicated by diagonal shading just below header l0. Combustion is substantially controlled by the amounts of coke and oxygen-containm as.

N early all of the available oxidant is consumed in the combustion zone, or flame front, thereby limiting the zone depth, e.g. to a few inches. A

The retort area below the combustion zone contains coke which is above its spontaneous ignition temperature but which, due to a lack of oxidant, does not burn. It is here that calcination takes place. Calcination time is controlled by varying retort depth and the rates of coke and oxidant input.

Steam and/or hydrocarbon are introduced into the retort area below combustion zone 12 through input pipe 14 and header 16. The heat, calcination gases and steam and/or hydrocarbon act to obtain the desired products, synthesis gases and cracked hydrocarbons.

Synthesis gases and cracked hydrocarbons are removed from the bottom of the retort area via conduit 22, flange 21 prevents solids from entering pipe 22. Vapor pump draws the product through conduit 22 and heat exchanger 24 cools the product before entering into condenser 26.

Vapor pump 20 creates a downward draft in the calciner to draw combustion gases through the hot coke.

Insulation in retort 6 prevents substantial heat loss. Cal- 0 cined coke is discharged from retort 6 through valve 28 without substantial loss of pressure.

FIG. 2 is a simplified horizontal schematic of a rotary hearth calciner showing feed chute 30 and valve 31 through which raw coke is fed. Oxidant is introduced at various points above and to the side of combustion zone 32 and calcination takes place in bed 34. Calcined coke is discharged from soaking pit 36. Combustion gases, e.g. N Ar, CO and H 0, are removed at the top of the calciner through stack 38.

FIG. 3 shows how the rotary hearth calciner is modified to effect the invention. Stack 38 has been closed off. Raw coke enters the calciner through feed chute 30 and valve 31 and is calcined in coke bed 42 below combustion zone 40. Combustion gases, including N Ar, CO H and H 0, are drawn through coke bed 42. Soaking pit 46 is lengthened to permit the cracking of hydrocarbons. Hydrocarbons and/or steam is introduced through valves 49 and into input pipes 48. Product gases, e.g. C H C H,,, etc. are drawn through protective flange 50, conduit 52, heat exchanger 54 via vapor pump 56.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The process of this invention is useful for calcining coke material. It is especially useful in calcining the so-called fluid" and delayed petroleum cokes and is preferably used for this purpose.

The oxidant used with the invention include fluorine, chlorine, nitrogen dioxide, and the like, but is preferably oxygen or mixtures thereof with inert gases. Examples of such mixtures include air, oxygen in superheated steam, etc. The oxidant can be preheated to any desired temperature prior to use in the process.

The amount of oxidant required in any particular instance will depend on the type of oxidant used, the coke to be calcined, the desired combustion zone temperature, the desired product gases, and the desired volatile combustible matter content of the calcined coke. This amount can be determined through routine methods.

Generally, however, the oxidant introduced into the calciner will be that amount required to completely oxidize only about 2 to 25 percent, by weight, of the coke being calcined. Preferably, sufficient oxidant is utilized to completely burn from about 5 to about 10 percent, by weight, of the coke charged.

The coke and oxidant input should be regulated to attain a temperature within the range of from about 2,000 to about 2,500 F., and preferably from about 2,200 to about 2,500 F.

In the retort calciner, the highest temperatures are obtained at the forward face of the combustion zone where most of the oxygen is consumed. There is a continuing slow temperature drop as the calcined coke moves away from this combustion front. For example, temperatures can range from about 2,500 F. in the calciner to about 1,000 F. in the area where coke is discharged and more preferably from about 2,450 to about 1 ,600 F.

Any hydrocarbon, liquid or gas, may be used with the invention. The type, state, and concentration of the hydrocarbon as well as the injection rate, will depend on many factors, including the products desired.

Some hydrocarbons have a negative heat of reaction which means that at high temperatures the desired product may be obtained with a comparatively small amount of heat absorbed from the calcined coke. Benzene and ethylene are examples. Other hydrocarbons, such as methane, ethane, propane, butane, pentane, and hexane, etc. have positive heats of reaction; they must absorb a greater amount of heat from the calcined mass in order to be effectively cracked.

Facts and figures relating to the combustion of hydrocarbons are plentiful. See, for example, Petroleum Refinery Engineering, 3rd Ed., 1949, McGraw-Hill, W. L. Nelson, Chapter V, Combustion, pp. 358-375, and Chemical Engineering Handbook, 3rd Ed., 1950, McGGRAW-hill, John H. Perry, Gaseous Fuels, pp. 1575-1589.

Steam may be introduced into the calciner separately or simultaneously with the hydrocarbon. It can be superheated prior to injection. lnasmuch as raw coke will have a certain moisture content, the amount and rate of steam injected will determine the extent of the water-gas reaction. The water-gas reaction serves to reform combustion gases within the calciner. This reaction can be calculated by known means to produce synthesis gases possessing specific characteristics. For background information see Industrial Chemicals, Faith, Keyes, and Clark, 2nd Ed. (1961), John Wiley & Sons, pp. 440444; and Chemical Process Industries, Shreve, McGraw- Hill (1956), pp. 88-89.

The following examples further explain the invention; they are not intended to limit the invention in any way. Rather, all equivalents obvious to those skilled in the art are meant to be included within the scope of the invention as defined in the specification and appended claims.

EXAMPLE I Six hundred and sixty-three lbs per square foot per hour (lbslft /hr) of raw coke containing 10 percent moisture is fed into a modified rotary hearth calciner where the temperature near the top of the soaking pit is about 2,500 F. Five hundred and sixty-six lbslft lhr of calcined coke are discharged at a temperature of about 1,600 F. No steam or hydrocarbons are added. Based on stoichiometric air to volatile ratios, lbslft lhr of gases are shown in Table 1.

Under the conditions of Example I, CH is introduced near the top of the soaking pit. Table 2 indicates the products of the reaction.

TABLE 2 Soaking Pit Outlet Product lbs/ftlhr lbs/fthr Coke 663 639 N, 856 856 Ar I4 14 C0 119 31 H 0 273 I65 CH, 128 32 H 0 36 CO 0 280 EXAMPLE lll About lbs/ft /hr of n-hexane at l00 F. is introduced into the process of Example I at a point above the 1,600 F. outlet and is cracked. The product gas removed at 1,000 F. contains methane, ethane, ethylene, etc. Examples of synthesis gases include methane, ethane, ethylene, and like products.

In addition, good yields of hydrogen and carbon monoxide can be obtained as illustrated in Example I].

What is claimed is:

1. In a calcination process comprising passing coke through a combustion zone in the presence of an oxidant wherein about 2 to about 25 weight percent of the coke is permitted to oxidize, thereby heating the remaining coke to a temperature within the range of about 2,000 F. to about 2,500 F. and producing combustion gases comprising N Ar, CO H O, CO, and H and then passing the heated coke through a calcination zone, the improvement comprising passing the combustion gases through the calcination zone and simultaneously introducing steam, hydrocarbon, or steam and hydrocarbon at a point below the combustion zone and at a temperature sufficient to obtain cracking of the hydrocarbon and removing the resulting synthesis gases, cracked hydrocarbons and calcined coke.

2. The process of claim 1 wherein the calciner is a retort calciner.

3. The process of claim 1 wherein the calciner is a rotary hearth calciner.

4. The process of claim 1 wherein the product gases and calcined coke are withdrawn from the calciner at a temperature within the range of from about 1,000 to about l,600 F.

5. The process ofclaim 1 wherein the hydrocarbon is alight naphtha.

6. The process of claim 1 wherein the hydrocarbon is a heavy naphtha.

7. The process of claim 1 wherein the cracked hydrocarbons comprise ethylene.

8. The process of claim 1 wherein the cracked hydrocarbons comprise acetylene.

" UNffED STAT1-$FATENT"GFFICE CERTIFICATE CORRECTION Patent No. 76,517 Dated uly 11, 1912 Inventofls) LaVaun S. Merrill, Jr. et a1 It is certified that error appears in the above-identified patent and thaL said Letters. Patent are hereby corrected as shown below:

7 Col. 1, line 15 j DeIeteW and insert '-N Col. 1, line 2s= Insert after ."drawn";

Col. 3, line 8: Delete "McGGraw-hill" and insert --McGrawHill-.

Signed and sealed this 28th day of November 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,J'R. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents 

2. The process of claim 1 wherein the calciner is a retort calciner.
 3. The process of claim 1 wherein the calciner is a rotary hearth calciner.
 4. The process of claim 1 wherein the product gases and calcined coke are withdrawn from the calciner at a temperature within the range of from about 1,000* to about 1,600* F.
 5. The process of claim 1 wherein the hydrocarbon is a light naphtha.
 6. The process of claim 1 wherein the hydrocarbon is a heavy naphtha.
 7. The process of claim 1 wherein the cracked hydrocarbons comprise ethylene.
 8. The process of claim 1 wherein the cracked hydrocarbons comprise acetylene. 